The present invention relates to electrical components and, more particularly, to the material design of the external surface of gas-discharge surge arresters.
Gas-discharge surge arresters have a variety of uses including the protection of telecommunication lines, for example. In this application surge arresters are used having electrodes with soldered-on, welded-on or integral leads. Such surge arresters may comprise two opposed electrodes and optionally a third, centrally located annular electrode. German Patent 28 28 650 discloses such a surge arrester. Like the electrodes, the leads attached to them are usually silver-plated if they are made of copper. Occasionally the use of tinned leads is required. In flow soldering the wetting of the leads is required during the soldering operation. If copper electrodes having welded-on copper leads are used, bronze (which is an alloy of copper and tin) may form near the weld when a tinned lead is welded to a copper electrode, weakening the weld mechanically and electrically. It is also known to use surge arresters without leads. With such arresters, the electrodes are contacted by spring action. It is also known to use surge arresters with alloyed-iron electrodes and to coat the electrodes with nickel. Moreover, it is common practice to apply identifying marks to the ceramic insulator of the surge arrester by imprinting it with symbols, numerals and letters.
There is a need for a surge arrester which can be manufactured at low cost and is suitable for automatic bulk processing without degradation of its insulating strength. There is also a need for a surge arrester that can be readily soldered into printed circuits or circuit boards.